Abstract: This paper proposes an adaptive unsymmetrical cross search pattern to perform fast block matching.The pattern solves the disadvantage of single pattern in searching vertical moving objects.It predicts the motion of the current block and chooses the pattern adaptively.This enables us to add the number of search points more efficiently and thus improves the search speed.Meanwhile，the new algorithm also adopts the advanced-stop criteria and linear search technology.Simulation results show that the new algorithm can reduce the search time above 20% compared with the UMHexagons algorithm adopted by H.264 standard.

Key words: motion estimation, UMHexagons algorithm, adaptive unsy-mmetrical cross search pattern

摘要： 提出了一种自适应十字形模板进行快速块匹配的方法。该方法解决了单一模板对于垂直运动宏块搜索的薄弱性，它提前预测当前块的运动，并根据预测结果自适应地选择十字形模板，因而能更有针对性地增加搜索点数，从而提高搜索速度。与此同时新算法还采用了提前终止准则和线性搜索技术。实验表明，新算法相比已被H.264标准采用的UMHexagons算法，编码速度提高了20%以上。

关键词: 运动估计, UMHexagons算法, 自适应十字形模板